The present invention relates to a delimbing and cutting head of a harvesting machine of the type having a body adapted to be mounted on a boom of the harvesting machine.
Currently used harvesting machines, harvesters, multi-process machines or equivalent are provided, as is known in the art, with equipment with which the trees are cut down, delimbed and cut to size. For functions like these, the machine is provided with a delimbing and cutting head mounted on a boom of the harvesting machine. It is standard practice to provide the delimbing and cutting head with grip arms to grip a tree trunk and with a chain saw or equivalent to cut the trunk. The grip arms are usually provided with a sharp edge so that they can simultaneously serve as delimbing blades. The delimbing and cutting heads are furthermore provided with drive rollers or wheels with a drive mechanism, which grip the trunk on opposite sides thereof and with which the trunk can be moved longitudinally so that when the trunk is being moved the delimbing blades can carry out the delimbing. Furthermore, modem delimbing and cutting heads are provided with measuring devices, such as a measuring wheel or wheels, with which lengths of the tree can be measured and determined. A selected length of the trunk can then be cut to size with the chain saw. In addition, the delimbing and cutting head is provided with rotating and turning machinery, with which said head can be turned as desired, and a tilting machinery or equipment, with which the delimbing and cutting head can be placed in desired position. The above functions are in general hydraulically operated.
On the delimbing and cutting head, drive wheels of various types are used. First, such drive wheels made entirely of metal are used that are provided with non-skid means, such as spikes, roughenings or the like. With such wheels a very good grip can be achieved to the trunk, but the grip of the wheels is highly aggressive so that considerable breaking of the timber and detaching of bark takes place. These in turn cause blueing of the timber and mold damage, requiring a greater use of chemicals in manufacturing paper and/or pulp.
To make the contact between the drive wheel and the trunk xe2x80x9csofterxe2x80x9d, a design has used in which the drive wheel comprises a hub made of metal, such as a sleeve-like hub, upon which a solid-rubber tire is fixed by curing. Since with a rubber tire of this type, no sufficient grip can be establish, non-skid means are arranged upon the rubber. Most frequently, said non-skid means comprise chains or chain nets attached to the flanges in the hub, or of chain nets tightened on top of the rubber layer. To further enhance the grip of the tire, the chains may be square or sharp in cross-section. On the other hand, the non-skid means may be composed of planar pieces with spikes or equivalent items arranged on top of the tire, said pieces being mountable on the flanges of the hub with the aid of chains. Furthermore, these can be, when using chains and chain nets, fixed to the wheel in a manner similar to that used in fixing non-skid chains on the wheels of work machines, that is, by tightening the chains or cables in the direction of the circumference.
A drawback and problem of rubber wheels provided with said non-skid means of the type described above relates to the attachment of the non-skid means on top of the wheel. That is, the non-skid chains and plates tend to turn and tilt on top of the wheel, which causes skidding and/or breaking and detaching of the tree bark, which damages the timber. Particularly in the spring, at so-called bast time, it is very important that a secure yet gentle grip of the trunk be obtained with the drive wheels of the delimbing and cutting head, because the layer on the trunk surface is soft and easily damaged.
The objective of the present invention is to provide a delimbing and cutting head for a harvesting machine, which includes drive wheels for gripping the trunk which will not cause damage to the trunk or will significantly reduce the amount of damage caused to the trunk as compared to the damage caused by conventional devices. To this end, the invention is mainly characterized in that the drive wheel is provided with fixing means arranged on the axial ends of the drive wheel so when that the chains are fixed to said fixing means and pretightened in place the compress the elastic material layer of the drive wheel in an axial direction.
As compared to the state of the art, the present invention also achieves the significant benefit that the drive wheels will not cause any substantial damage to the trunks or that the damage caused thereby to the trunks is significantly reduced. This is based on the inventive manner in which the chains forming the non-skid means have been arranged and at-tached to the drive wheel so that they remain in the position as intended, without turning or twisting, while allowing the elasticity required, which is provided by the rubber surface of the wheels. The other advantages and characteristic features of the invention are apparent from the detailed description of the invention herein.